Before birth, a fetus exists in a practically germ-free state, as the fetus is protected by the defense mechanisms of its mother. During parturition, the neonate is exposed to an abundance of bacteria from the mother's vaginal and skin flora as well as from the surrounding environment. Several weeks after its birth, the intestinal microflora of the neonate becomes established. The composition of this microflora is relatively simple and is believed to be influenced by the variety of bacteria the baby comes in contact with as well as the baby's diet.
In the first few months of life, an infant's diet consists mainly of human breast milk and/or formula. Human breast milk is well-known to contain more than 100 different oligosaccharides, some of which are genetically determined. Unfortunately, the structural similarities of many of the carbohydrates have made it difficult to isolate, identify and quantify these oligosaccharides.
Many beneficial functions have been attributed to human milk and its oligosaccharides. In fact, several studies have found that the stool of breast-fed infants differs from that of formula-fed infants. More specifically, studies have shown that stool from breast-fed infants has a lower pH, a higher proportion of bacteria of the genus Bifidobacterium, and a lower proportion of less desirable putrefactive-type bacteria than the stools from formula-fed infants. Studies have found that the low pH of human breast milk (5.0) inhibits the growth of Bacteroides spp., Clostridium, spp. and Escherichia coli (E. coli). (Beerens, H., et al., Amer. J. Clin. Nut. 33:2434-2439 (November 1980, this reference, as well as all other publications and patents disclosed herein, are incorporated by reference). Therefore, the breast-fed infant possesses a natural defense against Bacteroides, Clostridium, and E. coli, which gives the infant a resistance to gastroenteritis. Id. Furthermore, the introduction of cow's milk or formula into the diet of an exclusively breast-fed infant usually results in a substantial increase in the number of these bacteria. Petschow, B. W., et al., J. Clin. Microbio., 28:287-292 (1990).
Human breast milk is believed to contain certain factors which promote the development of a favorable intestinal bacterial flora, specifically, Bifidobacterium, which discourage the proliferation of pathogenic microbes. The growth of Bifidobacterium in the intestine of a baby is believed to be promoted by the physicochemical properties of human milk, particularly its high lactose content, which is a substrate for Bifidobacterium, its low protein content, and its low buffering capacity. Unfortunately, infant formula is believed to have a high buffering capacity which is not favorable for the growth of Bifidobacterium. Therefore, a need exists for a nutritional product for use in infants that promotes the growth and proliferation of favorable intestinal microflora such as for example, Bifidobacterium while inhibiting the growth of for example, Bacteroides, Clostridium, and E. coli.